(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Children's Library | Biodiversity Heritage Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
See other formats

Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

LUCIA AND ATREVIDA GLACIERS                            69
charge from Lucia Glacier seemed not appreciably larger than in 1909, although as the observations were made fully two weeks earlier than the junior author had ever been in Yakutat Bay before, and as snow still lay on the ground at sea level, the latter point could not be stated with certainty.
These scanty and tantalizing observations gave the impression that the advance of Lucia Glacier had not continued very long after our leaving the region ten months before or else that the rate of advance had slowed down so that changes were taking place very slowly indeed.
Stagnation in 1911. By the summer of 1911 the advance of Lucia Glacier was all over, for it was easily crossed by a Boundary Survey party in that year. The return to stagnation after the advance of 1909 was evidently quite as rapid as in the other glaciers of Yakutat Bay which have had advances stimulated by earthquake avalanch-ing. It was partly covered by ablation moraine when seen by the junior author from the bay in 1913.
General Description. Atrevida Glacier, which is much shorter than the Lucia, is an ice tongue of similar characteristics. It expands much more in its lower course, however, being only about a half mile wide in its deep mountain valley but flaring out rapidly to a mile and three quarters at the point where it passes between Amphitheatre Knob on the east and Terrace Point on the west, and coalesces with Lucia Glacier. The whole glacier, piedmont bulb and all, is probably less than ten miles in length. Several streams flow from it (a) to Kwik River, (b) directly to Yakutat Bay, and, (c) by Esker Stream, from the eastern side at the base of Amphitheatre Knob (Map 2).
Condition in 1890 and 1905. The glacier was named by Professor Russell in 1890,1 who described it in about the same terms as the Lucia, besides showing its condition by several pictures. The 1890 conditions seem almost exactly like those in August, 1905, when we obtained a bird's eye view of it from the summit of Amphitheatre Knob, which rises above its eastern margin, and later in August when one expedition was made in various directions over the ablation moraine near the east side and another, by the junior author, from the east side to Terrace Point and back by different routes.
The exact length of the glacier is not known, but the valley portion is probably less than five miles, while the distance from Terrace Point to the terminus of the piedmont bulb is about five miles more. There are numerous tributaries, all small, so far as seen, and descending in steep courses as cascading glaciers. In the lower portion of the valley there are cascading glaciers which no longer unite with the main glacier. The valley walls, which attain elevations of 5000 to 6000 feet, are everywhere steep, showing clear evidence of profound valley deepening by glacial erosion, and between them lies the glacier with a width of two or three miles, broadening toward the valley mouth. So far as observed in 1905, with a single small exceptional area, Atrevida Glacier was in a semi-stagnant state in its valley portion and quite stagnant on its outer portion beyond the mountain front. It was possible to travel easily on any part of the glacier and we walked freely over its surface. For a mile or a mile and a half within its mountain valley the glacier was covered with an almost continuous sheet of ablation moraine and the surface was an undulating waste of rock fragments of all sizes, from huge angular bowlders to
i Nat. Geog. Mag., Vol. in, 1891, pp. 92-5, and Plates 10 and 11.